1. Field of the Invention
The present invention relates to a 3-dimensonal display apparatus, and in particular to a 3D display apparatus and a method for optimizing the same.
2. Description of the Background Art
Generally, a 3D image capable of expressing 3 dimensions is obtained based on a remote distance of a stereo visibility using two eyes. Since two eyes are distanced by about 65 mm, a difference distance between two eyes is the most important factor in 3D images.
The left and right eyes see different 2D images, respectively. When two images are transferred to a brain through a retina, the brain recognizes the images for thereby reproducing the depth and actuality of a 3D image
In a method for viewing a 3D image, there are a glasses-wearing method and a non-glasses wearing method based on the use of glasses by a viewer.
The method of using glasses may be classified into an anaglyph method in which blue glasses and red glasses are worn, a density difference method for obtaining a 3D feeling by installing a filter having different transmittances at left and right glasses, a polarized glasses method of using polarized glasses having different polarizing directions, and a time division method of periodically repeating a time-divided image wherein a LCD shutter is installed in synchronization with the period. However, the method of using the glasses may cause inconveniences. In addition, there are some problems when viewing other objects except for the 3D image in a state that the glasses are worn.
Therefore, recently, the non-glasses method has been widely studied. Various applications have been developed. As representative methods of the non-glasses method that does not use glasses, there are a lenticular lens method that a lenticular lens plate is installed in front of an image panel wherein a cylindrical lens array is vertically arranged, and a parallax barrier method.
FIG. 1 is a view for describing a parallax barrier method; FIGS. 2A and 2B are views for describing a pitch computation formula of a parallax barrier; FIGS. 3A, 3B and 3C are views illustrating parallax barrier patterns in a conventional art; and FIG. 4 is a cross sectional view illustrating an assembling of a parallax barrier method in a conventional art.
As shown in FIG. 1, a parallax barrier 30 is installed in front of an image panel 20 wherein a transparent slit and a non-transparent portion are repeatedly arranged in the parallax barrier 30.
A viewer 10 views an image displayed on the image panel 20 through the transparent slit of the parallax barrier 30. The left and right eyes of the viewer 10 view other regions of the image panel 20 even when the eyes see through the same transparent slit. Namely, the left eye can see only L, L, L, L, L, . . . in the visible region 14 of the left eye, and the right eye can see only R, R, R, R, R, . . . in the visible region 14.
The parallax method is directed to using the above principle. Namely, in the parallax method, it is possible to view the images corresponding to the sub-pixels of other regions viewed through the transparent slit by the left and right eyes for thereby feeling a 3D effect. However, the conventional art may give a viewer a bad feeling to the viewer's eyes since a Newton ring phenomenon occurs.
As shown in FIG. 2A, the parallax barrier 30 is installed behind the image panel 20 at a certain distance D. The transparent slit is installed at an intermediate boundary portion of two sub-pixels R and L of the image panel 20. Therefore, the image of the sub-pixels R and L of the image panel 20 are shown at the position V through the transparent slit. When the image corresponding to the left and right eyes of the viewer are displayed on the image panel 20, the viewer can see the 3D image.
As shown in FIG. 2A, the parallax barrier 30 is positioned behind the image panel 20 in the parallax barrier method. At this time, the pitch S between the slits is computed based on the Equation S=2P(V+D) - - - (1) in the conventional art.
Here, S represents the slit pitch in the horizontal direction, and P represents the pitch of the sub-pixels R and L in the horizontal direction, and V represents the distance from the sub-pixels R and L and the viewer, and D represents a distance from the sub-pixels R and L to the parallax barrier 30.
As shown in FIG. 2B, the parallax barrier 30 is positioned in front of the image panel 20 in the parallax barrier method. The pitch S between the slits is computed based on the Equation S=2P(V−D)/V - - - (2).
However, when the Equations (1) and (2) are actually adapted to the products, there is a certain limit for developing and fabricating the optimized 3D products. Therefore, the equations need a certain supplement.
Namely, it is not optimized with the Equations (1) and (2) by the following reasons. First, only the straight property of light is considered. Second, the diffraction of light is not considered. Third, since the distances between the pixels of each element of the image panel 20 and the viewer 10 are different, the pitch S between the transparent slits should have a small difference.
In order to overcome the above problems, the tests are actually performed. As a result of the test, it is known that the common Equation of S=2P(V+D)/V should be changed to the Equation of S=2Pk(V+D)/V. In addition, it is known that the conventional common Equation of S=2P(V−D)/V should be changed to the Equation of S=2Ph(V−D)V. Here, k represents the value of a range of 0.98<k<1.00, and h represents the value of a range of 1.00<h<1.02. Therefore, it is possible to see the optimized 3D image.
Generally, it is recommended that the parallax barrier pattern should be designed with a width below ⅓ of the pixel with a straight transparent slit. In this case, the ghost is slightly decreased, but the brightness of the 3D image is decreased, and the dark Moire pattern appears in the vertical direction, so that the viewer may have a bad feeling.
FIG. 3A is a view illustrating the parallax barrier pattern in a conventional art. When an electrical signal is applied to the signal line 28, the non-transparent portion 32 gets darkened, and the rectangular transparent portion 34 operates as the slit. When the rectangular transparent portion 34 is adapted to the image panel 20, and the 3D image is viewed, the dark Moire pattern in the vertical direction as well as the dark Moire pattern in the horizontal direction appear, so that the viewer may have a bad feeling.
FIG. 3B is a view illustrating the parallax barrier pattern in another conventional art. When the pattern of the circular transparent part 36 is adapted to the image panel 20, and the 3D image is viewed, the light transmittance is decreased, and the dark Moire pattern in the vertical direction as well as the dark Moire pattern in the horizontal direction appear, so that the viewer may have a bad feeling.
FIG. 3C is a view illustrating another parallax barrier pattern in a conventional art. When the pattern of the rectangular transparent part 37 is adapted to the 3D image, and the 3D image is viewed, the light transmittance is increased, and the dark Moire pattern appears in the vertical direction. In addition, the light intensity distribution in the horizontal direction of the Moire pattern appears in a step shape and a dim rainbow shape, so that the viewer may have a bad feeling.
FIG. 4 is a cross sectional view illustrating an assembling of a conventional parallax barrier method. In the case that the parallax barrier 30 is a conventional electronic shutter 31, the image of the image panel 20 may be discolored due to the electronic shutter 31 based on the optical characteristic with the image panel 20. In order to overcome the above problem, a ¼ phase plate 25 may be attached. In addition, the polarized film 24 attached on the surface of the image panel 20 is processed with the surface reflection prevention, and a micro curve is formed on the surface of the same for thereby scattering light. Therefore, there is a big problem for viewing the 3D image.
In order to concurrently overcome the above problems, a ¼ phase plate 25 is attached. In this case, the cost of the ¼ phase plate 25 is high. When it is attached on the image panel 20, it is needed to accurately arrange the angle of the ¼ phase plate 25. In addition, in the case that the conventional electronic shutter 31 is attached on the image panel 20, when the surface of the ¼ phase plate 25 attached on the image panel 20 gets closer to the surface of the polarized film 23 of the rear surface of the conventional electronic shutter 31, a Newton ring phenomenon occurs. Therefore, the viewer may have a bad feeling.